Push button switches



y 3, 1960 w. E. DUMKE ETAL 2,935,577

PUSH BUTTON SWITCHES Filed Nov. 5, 1957 3 Sheets-Sheet 1 l/zvert 0 1/211 I MM? y 1960 w. E. DUMKE ETAL 2,935,577

PUSH BUTTON SWITCHES Filed Nov. 5. 1957 a Sheets-Sheet 2 1960 w. E. DUMKE ETAL 2,935,577

PUSH BUTTON SWITCHES Filed Nov. 5, 19s? s Sheets-Sheet s jdr/l/res 2 faz'feg United States Patent rosn BUTTON swrrcnas William E. Dumke and James R. Bailey, Chicago, Ill., as-

I signors to Switchcraft, Inc., Chicago, Ill., a corporation of Illinois Application November 5, 1957, Serial No. 694,666

11 Claims. (Cl. 200-18) The invention herein comprehends a push button switch assembly having a plurality of switching stations, which assembly may easily be modified so that it; will function with interlocking action or with an all-lock action or with a non-locking action as desired. The aforesaid interlocking or all-lock function may be combined with the non-locking function at one or more stations as desired.

The invention herein also comprehends the provision of means whereby a positive interlocking function may be provided in a single switch assembly, such'positive interlocking function being also provided where the switch assemblies are arranged in tiers.

A feature of the invention resides in the provision of a latch bar which cooperates with a push button plunger for each switching station, the latchbar being common to the switch assembly for any of the functions recited, and being capable of being indexed'to a position corresponding to either the interlocking or all-lock function. Ac-

, cording to the invention the assembly can be readily modified for either the interlocking or all-lock function by changing the position of a spring biasing the latch bar to the proper indexed position as determined by fixed guides for the bar engaging oneror the other end of a slotted opening in the bar. 7

Where the switch performs the interlocking function,

the spring is positioned so as to bias the latch bar witha desired load, the same spring being placed in another position on the switch frame and being loaded at another value to give a larger biasing force against the latch bar for all-lock operation of the switch.

A feature of. theinvention consists of the provision of a stop-plate which preferably can be positioned on theswitch frame at an end thereof remote from the biasing spring, to maintain an indexed position of the latch bar to achieve non-lock operation. In cases where movement of the latch bar is. achieved by a solenoid for release of the actuated stations, the aforesaid stope plate can be suitably positioned on the switch frame so as to limit the excursion of the solenoid armature. Irrespective of whether such solenoid is used for movement of the latch bar in releasing of the actuated stations, whether the latch bar is operating with an interlocking or all-lock function, such solenoid'can be employed without change for release of the stations for either function.

With the foregoing considerations in mind it is principal object of this invention to provide a push button actuated switch which can be'operated as an 11116110619. ing, all-lock or non-lock device, or operated with a combination of either of the first two with the third func- 2,935,571 Patented May 3, 1960 ICC tion, which functions can readily be obtained by slight adjustments to the assembly.

Another object is to provide a spring which can be positioned selectively on the switch frame to bias the latch bar at loadings corresponding to whether the switch is to operate with the interlocking or all lock function.

Another, object is to provide a push button switch having a positive interlock function to prevent the actuation of another station until an already actuated station is released.

Yet another object is to provide a switch assembly comprised of subassemblies arranged in tiers, and arranged so that the positive interlocking function can be transmitted from one tier to another.

Other objects and important features of the invention will be apparent from a study of the specification following taken with the drawings which together show a preferred embodiment of the invention and what is now considered to be the best mode of practicing the principles thereof. Other embodiments may be suggested to those having the benefitof the teachings herein, and such other embodiments are intended to be reserved as they fall within the scope and spirit of the subjoined claims.

In the drawings:

Fig. l is a plan view of a pushbutton switch, certain parts being broken away to show details thereof, said switch embodying the improvements according to the present invention, and being adjusted for a positive interlock function;

Fig. 2 is a view similar to Fig. 1, showing a portion of the switch of Fig. 1, and showing means for returning the plungers to the non-actuated position;

Fig. 3 is an elevational view taken along the line 33 of Fig. l and looking in-the direction of the arrows;

Fig. 4 is an endview of the switch assembly seen in Fig. 1, said view being taken in the direction of the arrows 44 of Fig. l; V

Fig. 5 is an elevational view of a positive interlocking device for the switch of Fig. 1, said view being taken taken looking in the direction of the arrows 5-5 of Fig. l; I

Fig. 6 is a perspective view of a spring for biasing the latch bar of the assembly of Fig. 1, said spring being selectively loaded according to whether the switch of Fig. l is to have the all-lock or interlock function;

Fig. 7is an elevational view showing the switch assembly of Fig. 1 arranged in tiers for a positive interlocking action for each of the tiers of the assembly.

Fig. 8 is a detailed elevational view of structure for transmitting the positive interlock function from one tier of the assembly seen in Fig. 7 to another tier;

Fig. 9 is a view similar to Fig. 1, to an enlarged scale, and showing the switch according to the present invention arranged for operation with an all-lock function; and

Fig. l0'is an enlarged plan view showing the operation of latching means cooperating with the latch bar when the plungers at a switching station are moving to the actuated position.

Referring now particularly to Figs. 1 to 3 of the drawings, the improved switch according to the present invention is referred to generally by the reference numeral 20, and comprises a frame 21 consisting of a channel shaped front frame member 22 and a similar channel shaped rear frame member 23 spaced therefrom. Each end of the frame members 22 and 23 is provided with an aperture 24 through which protrudes an car 26 of a spacer member 27, spacer 27 having a shoulder bearing against the inner facesof the frame members 22 and 23 so as to maintain them a fixed distance apart. Channel shaped cross frame members 28 are spaced a slight amount from the spacer members 27, and each of the cross frame members 28 has a slot 29 near. theend thereof toreccive 3 an ear 31 extending from webs 32 of the front and rear frame members 22 and 23, see particularly Fig. 2.

Each cross member 28 is secured to the spacer member 27 by means'of screws 33, see also Fig. 9, which are threaded into the spacer 27, there being washers 34 maintaining the spacer 27 and the cross frame member 28 in properly spaced relationship. Each cross member 28 has mounting lugs 36 at each end thereof, so that the frame assembly thus far described can be bolted or otherwise secured to a piece of apparatus as desired.

The frame members 22 and 23 afford a support for a number of plungers 37 having a push button or knob 38 at the end thereof. Plungers 37 are guided in slots 39 formed in the webs32 of the frame members 22 and 23, and are biased to a released position by means of a spring 41, one end of which bears against the web 32 of the back frame member 23, and the other end of which bears against a shoulder 42 on the plunger 37, see also Fi 3.

The plunger 3'7 affords a support for switch actuators 43, each being carried on a'shaft 44 extending laterally of the plane of the plunger 37. The switch actuators 43 are arranged to cooperate with a switch assembly indicated generally by the reference numeral 49, see Fig. 3, adapted to be mounted upon a support plate 46 held by screws 47 to a flange 48 of the cross frame members 28; As seen in Fig. 3, such a support plate 46 is mounted both on the top and'bot-tom sides of the switch 20, and switch assembiy 49, which is merely a typical switch assembly, can be arranged on both support plates 46 at each of the plungers 37 for any desired kind of a switching operation. I

The plungers 37 in moving to the actuated position cooperate with a latch bar indicated generally by the reference numeral 51. Latch bar 51 is supported at its ends upon the spacer members 27 and the cross frame members 28, and extends through slots 52 and 53 formed respectively therein. Additionally, the latch bar 51' is supported upon a spacer member 54 extending between the front frame member 22 and the rear frame member 23, see also Fig. 9, the spacer member 54 having a slot 56 therein, at which point the latch bar 51 is supported.

The latch bar 51 is provided at each end, with a slot 57, the ends of the slot 57 being semi-circular as shown at 58. The latch bar 51 is guided at the slots 57 by means of a roller 59 mounted upon a shaft 61 supported by the flanges 48 of the cross frame members 28. At least one of the slots 57 has a critical longitudinal dimension which determines the excursion of the latch bar to its two indexed positions. The latch bar accordingly has an indexed position to the right as seen in Fig. 9 at which time the switch 20 functions as an all-lock device, or to the left as seen in Figs. 1 and 2 at which time the switch functions as an interlock device. a

The latch bar 51 is biased to the left as seen in Fig. 1 by means of a spring 62, see also Fig. 6, formed substantially in the shape of a U with spaced limbs 63 bent back upon themselves to form arms 64, each of the arms 64 havinga lateral extension 66 therefrom received in punched out openings 67 in the flange 48 of the cross member 28. The spring 62 has a portion 69 which bears against a shoulder 71 formed in the end at the latch bar 51. When mounted as seen in Fig. 1, spring 62 biases the latch bar 51 to the left, the permissible movement of the latch bar 51 being limited by one end of the slot 57 at the semi-circular portion 58 thereof which engages the roller 59. I Each of the plungers 37 supports a plunger pin 76 retained in position against the plunger 37 by means of a pair of arms 77 of a U-shaped spring clip 78 riveted to the plunger 37 by rivets 79. Each of the spring arms 77 has a generally U-shaped saddle 81 near the ends thereof in which the pin 76 is disposed, the bias of the spring arms 77 forcing the pin against the plunger 37. As seen in Fig. 3' particularly, the plunger 37 has a long 4 slot 82 therein through which the latch bar 51 extends, and the plunger pin 76 accordingly bears against the plunger 37 at portions 83 on'the pin 76 flanking the aperture 82.

As seen in Figs. 1 to 4 inclusive, the switch assembly is arranged to functionas an interlocking device. That is to say, the actuation of any plunger 37 causes a previously actuated plunger to be released. When the plunger 37 is moved to the actuated position the plunger pin 76 moves over a camming surface 84 formed in punched out openings 86 located at each plunger in the latch bar 51, see again Fig. 9. In moving over the camming surface 84 the latch bar 51 is shifted a slight amount to the right, and further movement of the plunger 37 causes the plunger pin 76 to enter a locking slot 87 the latch bar 51, see also Fig. 10. The aforesaid shifting movement of the latch bar 51 causes'a previously actuated plunger to move to the released position by reason of the spring 41. At the completion of the actuating operation the spring 62 urges the latch bar 51 to the left, as seen in Fig. l, to maintain the plunger pin'76 in the locking slot 87, the latch bar at such time being urged by the bias of the spring 62 against the right hand semi-circular end 58 of the left hand slot 57.

The aforesaid interlock function of the switch can be accomplished by the simultaneous operation of a number of plungers 37, which simultaneous operation would be accompanied by the release of a previously actuated plunger. Under, certain conditions it 'is-desirable that only oneplunger 37 be actuated at a time, and means are accordingly provided which prevents the simultaneous operation of more than one plunger.

Accordingly, there is provided a cage or race 88 having end walls 89 contiguous with a lug 91 for mounting to the mounting lug 36 by means of a bolt 92 shown. The race 88 is arranged to hold a plurality of balls 93, the total clearance of the balls in the race 88 being but little more than the thickness of a plunger 37. When a plunger 37 is actuated, it can move between a pair of contiguous balls 93, at'which time there is not suflicient All of the plungers can be moved to the released positionby an incomplete actuation of any of the stations including its plunger 37. That is to say, the plunger pin 76 in moving over the camming surface 84 will cause translative movement of the latch bar 51 to release the previously actuated plunger, and if the actuating movement 'is not completed such partially actuated plunger can move to the released position with all the other plungers also being in the released position.

However,'the latch bar may be shifted to' the right, as seen in Fig. 1, to cause release of an actuated station by means of a solenoid 94 having an armature 96 of the pusher type arranged to shift the latch bar 51 to the right. 'The solenoid 94 is mounted upon a bracket 97 held to'the web of the channel shaped cross member 28 by any convenient means. Alternately, the solenoid 94 can be mounted at the right end of the assembly seen in Fig. 1, such a solenoid being of the pull type, to shift the latch bar 51 to the right to release the actuated stations.

Each of the positive interlock means 88 and 93 forthe switch assembly'seen with reference to Figs. 1 to 4 inclusive, canbe arranged by means as will be described whereby suchpositive interlock function can be had with a plurality of switch assemblies arranged in a tiered relationship as seen with reference to Figs. 7 and 8. As seen particularly in Fig. 7, each assembly 20 can be connected in a tier to another assembly 28 by means of a spacer member 101 having an upper lug 102 connected by bolt and nut means 103 to the flange of the cross member 28. The lower end of the spacer member 101 likewise has a lug 104 connected by bolt and nut means 106 tothe upper flange of the cross member 28, such spacer members 101 being bolted to the switch assembly in the manner shown to provide any desired number of tiered switch assemblies.

Consider now an actuated plunger 37 occupying the position seen in Fig. 7 between contiguous balls 93 to take up the clearance between the balls 93 held in the race 88 seen particularly with reference to Figs. 1 to 5 inclusive. In such actuated position of the plunger 37, as has been described, it is not possible to actuate another plunger 37 until the already actuated one has been released. g

, Means are provided whereby none of theplungers 37 in the other tiers seen in Fig. 7 can be actuated until an actuated station or plunger 37 has been released. There is accordingly provideda pin 107 having its upper end tapered as at 108 to contact the spherical surfaces of a pair of contiguous balls93. Pin 107 passes through a slot 105 in the topmost race 88 and is guided in an eye 109, see also Fig. 8, held by rivets 111 to a strap 112 held at its ends between the lug 102 and the cross frame member 28 by the securing means 103.

The lower end of the pin 107 is likewise tapered as at I 113 to contact the surfaces of a pair of contiguous balls 93 of the next lower tier or assembly 20. The lower end of; the pin 107 passes through a slot 110 in the upper surface of the race 88, is likewise guided at the lower tier 20 by means of eye member l09 secured in the same fashion to the strap 112 which is secured at its ends between the lower lug 104 of the spacer member 101 and the upper flange of the cross member 28 by the a securing means 106. .The eye members enable the pins to have displacement along-their longitudinal axis both translatively and angularly according to the displacement of the balls 93. 7

When the uppermost tier has an actuated plunger 37, such plunger will urge the balls 93 contacting the tapered surface108 together, thereby resulting in a camming action displacing the tapered pin 107 both downward and angularly to force the balls 93 in contact with its lower tapered surface 113 apart. The dimensions of the tapered surface 113 and the length of the ball race 88 and the dimensions of the balls 93 at such lower tier are such as to prevent a plunger 37 of such lower tier to be actuated, since allof the clearance has been taken up by the tapered surface 113. i Likewise, when the tapered surface 113 takes'up the clearance between the balls 93 of the lower tier the tapered surface of the pin 107 cooperating with the next lower tier will contact the balls 93 to urge such pin in a direction to constrain the balls 93 of such next tier.

. It is believed evident that the actuation of a plunger" 37 in any tier can transmit the locking function described by'means of the pins 107 to tiers located both above and below such tier where the plunger 37 is actuated.

The switch described with reference to the preceding figures can be modified so that it can perform with an all lock function, that is to say, one or more of the plungers 37 can be actuated without effecting the release of a previously actuated plunger.

Referring now particularly to Figs. 9 and 10 of the drawings, the latch bar 51 is urged by the spring 62 to the right, the spring 62 having previously been transferred from the right end to the left end of the frame assembly, to a position where the roller 59 at the left end of the latch bar 51 is in contact with the left hand end of the slot 57. The spring 62 in the position shown in Fig. 9- has its element 69 in contact with the left end of the latch bar 51. In positioning the spring 62 as seen inFig. 9, it is loaded a greater amount than in the position seen in Fig. l at the opposite end of the switch frame for a purpose as will now appear.

7 Each of the plungers 37 in moving to the actuated position when the latch bar 51 is in the position seen with respect to Fig. 9 has its latch pin 76 move over a surface 117 spaced from the camming surface 84 at the opening 86 in the latch bar 51. As the plunger pin 76 contacts the surface 117 it moves away from the plunger 37 until it enters a slot 118 extending in the manner shown at the opening 86, at which point the plunger 37 is locked.

It may be noted that a number of stations or plungers 37 can be simultaneously actuated, or that the stations can be actuated one at a time without releasing a previously actuated station. The load in the spring 62 is accordingly made greater to prevent any translating shift of the latch bar 51 to the left, as might be occasioned by having too small a load in the spring 62. -Such shift would release already actuated stations. It will be noted that spring 62 is strained a greater amount when placed at the left end of the frame than at the right end.

Release of the actuated plungers during the all lock functionof the switch assembly, as has just been described, is achieved by a release station seen in Fig. 9, the plunger 37 of such release station supporting a pair of plunger pins 76, one each side of the plunger 37. The left hand plunger pin 76 of the release station carries a roller 119 arranged to contact a surface 121 in the latch bar 51 to shift the latch bar to the left against the bias of the spring 62, thereby to release the previously actuated stations.

As contrasted to Fig. 1, the solenoid 94 can be arranged to have its armature 96 connected at 122 to the left hand end of the latch bar 51 to shift it to the left, the solenoid 94 in such case being of the pull type. In the usual case, however, solenoid 94 is connected to the other end of latch bar 51.

I The switch according to the present invention may also have its latch bar 51 indexed so that each of the plungers 37 may be momentarily actuated and released for actuation'of a switch assembly at such plunger. To this end a stop-plate is positioned on the cross'frame member remote from the spring 62 so that the latch 51 is in a position where the plunger pins 76 do not contact surfaces 117 or 84. When the spring 62 is positioned as seen in Fig. 1, such centering of latch bar 51 is achieved by a stop-plate 72 held by screws 73 to the web of left hand cross member 28. The stop-plate "l2 bears against a shoulder 75 of a cut out portion 74 at the left hand of latch bar 51. At such time the latch bar 51 is properly centered for momentary actuation of plungers 37.

A stop-plate 126 may also be mounted at the right 4 hand cross member 28 when the spring 62 is supported at the left end of the switch assembly for all-lock operation, as seen in Fig. 9. Referring now to Fig. 1, during at the right hand end of latch bar 51 to engage a shoulder 124 of such cut out portion 123.

As described with reference to the other position of spring 62, the plunger pins 76 move in opening 86 of latch bar 51 between the spaced surfaces 117 andf84.

The switch may also, for either the interlock function or the all lock function described, be arranged for only momentary actuationof any desired station by removal of the plunger pin 76 at such station.

From the description foregoing it is believed evident that there has been provided a new and useful improvement in the art of push button switching. As has been described, the latch bar 51 is indexed to proper position merely by changing the position of a spring from one end of the switch frame to the other, the spring in the interlock function of the switch having a lower biasing value than when in the position corresponding to all-lock operation. The switch according to the present invention may also be made as part of a tiered assembly where positive interlock can be had between the switch assembly at any tier. In cases where a large number of switch '7 ing stations may be provided it is possible to insure that only one station can be actuated at a time.-

While the invention has been described in terms of a preferred embodiment thereof its scope is intended to be limited only by the terms of the claims here appended.

We claim as our invention:

1. In a push button switch selectively adjustable for all lock and interlock operation, a frame, a plurality of switching stations including a plunger at each switching station movable with respect tosaid frame to and from ac tuated positions, a latch bar supported on said frame, and

means for indexing said latch bar to positions determina tiveof all-lock and interlock operation of said push button plungers comprising cooperating spaced and fixed means for limiting the excursion of said latch bar to positions corresponding to all-lock and interlock operation, a spring attachable to said frame at one end thereof and engaging said latch bar at a position whereby said spring is strained to bias said'latch bar at a first biasing value for interlock operation, said spring being attachable to said frame at the other end thereof and engaging said latch bar at a position whereby said spring is strained to bias said latch bar at a second higher biasing value for all-lock operation.

2. In a push button switch selectively adjustable for all lock and interlock operation, a frame, a plurality of switching stations including a plunger at each switching station movable with respect to said frame to and from actuated positions, a latch bar supported on said frame, and means for indexing said latch bar to positions determinative of all-lock, interlock and non-lock operation of said push button actuators comprising cooperating spaced and fixed means for limiting the excursion of said latch bar to positions corresponding to all-lock and interlock operation, spring means attachable to said frame at one end thereof for biasing said latch bar at a first biasing value of said spring means for interlock operation, said spring means being attachable to said frame at the other end thereof for biasing said latch bar at a higher second biasing value for biasing said latch bar in an opposite direction to a position for all-lock operation.

3. In a push button switch selectively adjustable for all lock, interlock and non-lock operation, a frame, a plurality of switching stations including a plunger at each switching station movable with respect to said frame to and from actuated positions, a latch bar supported on said frame, means for indexing said latch bar to positions determinative of all-lock, interlock and. non-lock operation of said push button actuators comprising at least one slot in said latch bar of a longitudinal dimension corresponding to limited excursion of said latch bar vto 7 positions corresponding to all-lock and interlock operation, means cooperating with said spaced slot for limiting the excursion of said latch bar, spring means attachable to said frame at one end thereof for biasing said latch bar to one positionfor interlock operation, said spring means being attachable tosaid frame at the other end thereof for biasing said latch bar in an opposite direction to a position for all-lock operation.

4. The invention as defined in claim 3 wherein a stop member is secured to said frame remote from the spring, and wherein means. are provided in said latch bar for engagement. by said stop member for indexing of the same for non-lock actuation.

5. In a push button switch selectively adjustable for all lock and interlock operation, a frame, a plurality of switching stations including a plunger at each switching station movable with respect to said frame to and from actuated positions, a latch bar supported on said frame, means for indexing said latch bar to positions determinative of all-lock, interlock and non-lock operation of said push button actuators comprising a pair of spaced slots in said latch bar, means cooperating with said lib sion of said latch bar to index'positions corresponding to all-lock and interlock operation, means cooperating with the said one slot and determining the aforesaid index position, and'spring means biasing said latch bar against said last named means ina direction determinative of Whether said latch bar'is indexed for interlock or all-lock operation.

6. In a push button switch selectively adjustable for all look and interlock operation, a frame having a plurality of switching stations thereon, a push button plunger 'at each switching station, latching means supported by said plungers, a latch bar supported by said frame and having a pair of spaced latching surfaces at each switching station, means for indexing said latch bars to positions determinative of all lock and interlock operation of said push button plungers comprising cooperating spaced and fixed means for limiting the excursion of said latch bar to the positions corresponding to all lock and interlock operation, said latching means shifting said latch bar to release a previously actuated station when said latch bar is indexed for interlock operation, said latching means moving relative to one of said spaced latching surfaces when said latch bar is indexed for all lock operation, and a spring attachable to said frame at one end thereof and engaging said latch bar at a position whereby said spring is strained to bias said latch bar at a first biasing value for interlock operation, said spring being attachable to said spring at the other end thereof and engaging said latch bar at a position whereby said spring is strained to bias said latch bar at a second higher biasing value for all lock operation.

a 7. In a push button switch selectively adjustable for alllock and interlock operation, a frame havin a plurality of switching stations thereon, a push button plunger at each switching station, latching means supported by said plungers, a latch bar supported by said frame and having a pair of spaced latching surfaces at each switching station, means for indexing said latch bar to positions determinative of all lock and interlock operation of said push button plungers comprising cooperating spaced and fixed means for limitin the excursion of said latch bar to the positions corresponding to all lock and interlock operation, said latching means moving with a push button plunger and not relative thereto for shifting said latch bar to release a previously actuated station when said latch bar is indexed for interlock operation, said latching means moving with said push button plunger and relative thereto over one of said spaced latching surfaces when said latch bar is indexed for all lock operation, spring means attachable to said frame at one end thereof for biasing said latch bar in one direction at a first biasing value of said spring means for interlock operation, said spring means being attachable to said frame at the other end thereof for biasing said latch bar in an opposite direction to a position for all lock operation at a higher second biasin value of said spring means.

8. A push button switch assembly comprising a plurality of tiered switch assemblies, each of said switch assemblies comprising a frame, a plurality of plungers movable with respect to said frame to and from actuated positions, a latch bar holding a plunger in actuated position and adapted to release a previously actuated plunger when another plunger is actuated to a latched position, and means for preventing the simultaneous actuation of more than one plunger in the same or different tiers comprising a race at each switch assembly having a plurality of roller members therein, the total clearance between said roller members being but little more than the thickness of a plunger at a switching station, and means for closing the clearance between the roller members'of an adjacent tier comprising a pinhavin a first tapered end contacting contiguous roller members of a race in one tier, and a second tapered end contactin contiguous roller members of an adjacent tier, said tier being unconstrained between its ends and being displaced along its longitudinal axis both translatively and angularly by the roller members of one tier to close the clearance between the roller members of the adjacent tier when the plunger is actuated at a tier.

9. A push button switch assembly comprising a plurality of tiered switch assemblies, each of said switch assemblies comprising a frame, a plurality of plungers movable with respect to said frame to and from actuated positions, a latch bar holding a plunger in actuated position and adapted to release a previously actuated plunger when another plunger is actuated to a latched position, and means for preventing the simultaneous actuation of more than one plunger in the same or dilferent tiers comprising a race at each switch assembly having a plurality of balls therein, the total clearance between said balls being but little more than the thickness of a plunger at a switching station.

10. A push button switch assembly comprising a plurality of tiered switch assemblies, each of said switch assemblies comprising a frame, a plurality of plungers movable with respect to said frame to and from actuated positions, a latch bar holding a plunger in actuated position and adapted to release a previously actuated plunger when another plunger is actuated to a latched position, and means for preventing the simultaneous actuation of more than one plunger in the same or different tiers comprising a race at each switch assembly having a plurality of roller members therein, the total clearance between said roller members being but little more than the thickness of a plunger at a switching station, and means for closing the clearance between the roller members of the tiers remote from the tier in which there is an actuated plunger comprising a pin having a first tapered end contacting contiguous roller members of a race in one tier and a second tapered end contacting contiguous roller members of an adjacent tier, said pin being unconstrained between its ends and being displaced along its longitudinal axis both translatively and angularly by the roller mem- 10 bers of one tier to close the clearance between the roller members of the adjacent tier when the plunger is actuated at a tier.

11. A push button switch assembly comprising a plurality of tiered switch assemblies, each of said switch assemblies comprising a frame, a plurality of plungers movable with respect to said frame to and from actuated positions, a latch bar holding a plunger in actuated position and adapted to release a previously actuated plunger when another plunger is actuated to a latched position, and means for preventing the simultaneous actuation of more than one plunger in the same or different tiers comprising a race at each switch assembly having a plurality of balls therein, the total clearance between said balls being but little more than the thickness of a plunger at a switching station, and means for closing the clearance between the balls of the tiers remote from the tier in which there is an actuated plunger comprising a pin having a first tapered end contacting contiguous balls of a race in one tier, and a second tapered end contacting contiguous balls of an adjacent tier, said pin being unconstrained between its ends and being displaced along its longitudinal axis both translatively and angularly by the balls of one tier to close the clearance between the balls of the adjacent tier when the plunger is actuated at a tier. 1

References Cited in the file of this patent UNITED STATES PATENTS 679,310 Hall July 30, 1901 2,200,076 Cooper May 7, 1940 2,414,307 Johnson Jan. 14, 1947 2,831,075 Dunke et a1 Apr. 15, 1958 FOREIGN PATENTS 207,016 Great Britain Nov. 22, 1923 304,819 Great Britain Jan. 28, 1929 693,593 Germany July 15, 1940 

